Rosuvastatin and its pharmaceutically acceptable salts were first disclosed in U.S. Pat. No. 5,260,440. It also discloses process for their preparation.
U.S. Pat. No. 6,875,867 disclosed a process for the preparation of HMG CoA reductase inhibitors through Julia modified-olefination reaction.
The alternate process for the preparation of rosuvastatin is disclosed in U.S. Pat. No. 6,844,437. The disclosed process involves the condensation of diphenyl[4-(4-fluorophenyl)-6-isopropyl-2-[methyl(methylsulfonyl)amino]pyrimidin-5-ylmethyl]phosphine oxide with tert-butyl-2-[(4R,6S)-6-formyl-2,2-dimethyl-1,3-dioxan-4-yl}acetate in presence of a base in a suitable solvent to provide tertiary butyl ester compound of rosuvastatin which is further converted into free acid or salt by conventional methods.
The United States patent application number US 2005/0124639 disclosed another alternate process for the preparation of rosuvastatin and its intermediates through wittig reagents. The disclosed process involves the condensation of wittig reagent like triphenyl[4-(4-fluorophenyl)-6-isopropyl-2-[methyl(methylsulfonyl)amino]pyrimidin-5-ylmethyl]phosphonium bromide or other reagent with tert-butyl-2-[(4R,6S)-6-formyl-2,2-dimethyl-1,3-dioxan-4-yl}acetate in a suitable solvent in presence of a base to provide tertiary butyl ester compound of rosuvastatin which is further converted into free acid then to calcium salt by contacting with a calcium source.
The amorphous form of rosuvastatin calcium prepared as per the disclosed process (i.e., through crystalline methyl ammonium salt) in U.S. Pat. No. 6,841,554 having the purity of more than 99.85%. The later patents like US2005/080134, WO 2005/040134 and WO 2007/086082 claim amorphous rosuvastatin calcium with high purity.
The statins are very important inhibitors of the HMG CoA reductase; hence there is a need to develop a novel cost effective process for their preparation.
Accordingly the present invention provides a novel process for the preparation of statins and their pharmaceutically acceptable salt compounds through novel intermediates which are more effective and easy to scale up in commercial batches in a convenient and cost effective manner.